The spinal column has many functions including supporting the body, weight transfer, motion, and protection of the spinal cord and the nerve roots The spinal column is a structure composed primarily of bones, ligaments, muscles, and cartilage. The bones of the spinal column are called vertebrae.
As the population ages, it is anticipated that there will be an increase in adverse spinal conditions which are characteristic of weakened bone. Also, with aging come increases in spinal stenosis, which is characterized by thickening of the bones, which make up the spinal column and facet arthropathy. These degenerative conditions as well as physical trauma can lead to failure or instability of the spinal column. Spinal stenosis is characterized by a reduction in the available space for the passage of blood vessels and nerves.
Spinal stenosis in the neck results in a reduction foraminal area (i.e., the available space for the passage of nerves and blood vessels) which compresses the cervical nerve roots and causes radicular pain. Humpreys, S. C. et al., Flexion and traction effect on C5-C6 foraminal space, Arch. Phys. Med. Rehabil., vol. 79 at 1105 (September 1998). Another symptom of spinal stenosis is myelopathy, which results in neck pain and muscle weakness. Id. Extension and ipsilateral rotation of the neck further reduces the foraminal area and contributes to pain, nerve root compression and neural injury. Id.; Yoo, J. U. et al., Effect of cervical spine motion on the neuroforaminal dimensions of human cervical spine, Spine, vol. 17 at 1131 (Nov. 10, 1992). In contrast, neck flexion increases the foraminal area. Humpreys, S. C. et al., at 1105. Pain associated with stenosis can be relieved by medication and/or surgery. Accordingly, there have been developed surgical procedures and implants for alleviating conditions such as spinal stenosis, vertebral fracture and other spinal injury.
Placement of spinal implants requires surgery. Open surgery for placement of spinal implants requires a lengthy hospital stay and an extended convalescence. Open surgery also carries increased risk of infection and other complications. Of course, it is desirable to eliminate the need for major surgery for all individuals and in particular for the elderly. Accordingly, there is a need to develop procedures and implants for alleviating degenerative conditions of the spine which are minimally-invasive, can be tolerated by the elderly and can be performed preferably on an outpatient basis.
Minimally-invasive procedures typically access the site of the spinal intervention through small incisions. Minimally-invasive procedures reduce trauma to the tissue thereby reducing hospital and convalescence time and reducing the risk of complications. However, many implants for minimally-invasive spinal interventions must be assembled prior to insertion, thus requiring larger incisions for insertion. Also, once assembled, the size of the implant cannot be changed inside the patient. If a larger implant is required, the smaller implant must first be removed and a new larger implant inserted.
In view of the foregoing background, it would therefore be desirable to have a spinal implant that could be assembled in situ inside a patient.
It would also be desirable to have a spinal implant system wherein the size of the implant may be adjusted during the procedure depending on patient anatomy without removal of the implant.
It would still further be desirable to have a minimally-invasive surgery procedure for installing an implant that could be assembled in situ inside a patient.